1. Field of the Invention
This invention relates to an ultrasonic vascular surgical system, and more particularly to an ultrasonic surgical system having a low frequency velocity transformer that is provided with a coupling unit with an untuned guide wire.
2. Description of the Prior Art
One prior art ultrasonic surgical system is described in U.S. Pat. No. 4,920,954 which issued on May 1, 1990. In that system, a generator has a lead for connection to a power supply with a handpiece having a lead connected to the generator. A velocity transformer is driven by the generator and has a vibration end portion with a guide wire having an inboard end connected fixedly to the vibratory end portions.
Another system is described in U.S. Pat. No. 4,920,954 as having a metal, composite guide wire comprised of a plurality of long thin wires of platinum, titanium and other exotic alloys which are combined to form the composite guide wire. This type of multi-alloy composite guide wire is used extensively in CAT labs for reaching remote areas in the human body, typically a lesion within an artery or vessel. Although insertion of this composite guide wire requires a skilled professional who has the ability to maneuver the tiny composite guide wire through a maze of channels and branches, the insertion of the composite guide wire can at times lead to difficulties that and therefore increase the risk of exposure to harmful x-rays to both patient and professional during angioplasty procedures. An attempt to speed up this operation can hamper ability of a surgeon and/or a practitioner.
Another system employs a different type of guide wire which is formed in increments to control change its bending characteristics, providing a means for protecting the vessel from perforation through increased flexibility of the wire. These increments are metal and are bonded usually by electron beam welding of dissimilar materials, or through brazing, to combine different bending characteristics . The tip of such a guide wire is usually composed of a central core of wire alloy, and around it as fine hair-like wire is spun, forming a soft spring located at the tip of the guide wire. This spring-like tip is as soft as a sponge and buckles easily through its own weight thereby providing rapid, easy passage through some of the most intricate of curves within the human body.
When one of the aforementioned guide wires is used in angioplasty procedures, it is introduced into a blood vessel via an introducer. The wire becomes almost life-like as each centimeter of it is pushed through the introducer and into the vessel. It makes its way toward a branch or another final destination (possibly a partial obstruction or any other biological malformation needing to be reached for diagnosis). It may be possible when manipulating the guide wire, due to necessary twisting and shoving, for an incorrect channel to be reached. Perhaps the wire may get jammed into a tight obstruction where the tip can actually buckle and can appear like a knot under fluoroscopic conditions. Any attempt to release the tension of the wire may in fact cause damage to the fine coil of wire which allows the tip to contact fragile blood vessels.
A further prior art system has a guide wire which is a heat-sensitive composite guide wire, where the guide wire is formed with several different metals combined in a manner that such wire material is formed as a semicircle or other portion of a circle, and combined axially to complete a full circular cross section. Each section of the wire is adhered together to permanently construct a straight member at room temperature. If heat is applied to different segments along the length of such a guide wire, the heating will cause bending of the wire due to the different coefficient of expansion of each of the materials bonded. By controlling the duration and the amount of energy applied to the composite guide, different bending angles may be acquired. Cooling the composite guide wire will cause the guide wire to bend in the opposite direction, allowing multi-curvature lumens to be entered. To combine a multi-temperature guide wire system that not only bends in one direction from its equilibrium position at room temperature and in the complete opposite position when cooled, seems to implant a greater degree of difficulty to the practicing CAT specialist.
Yet another prior art system has a guide wire which provides a unidirectional temperature change. Such a guide wire has a single heating element which is fabricated into the abovedescribed composite guide wire with little difficulty. Such a wire still maintains the flexibility and small cross sectional area needed to cross tight lesions. The heating element may include pieces of nichrome wire imbedded into the guide wire, with one length insulated from the other but both extending from one end to the other; or it can include a single strand of nichrome wire with the strand being insulated from the guide, along its total length, but attached to the far end of the guide making a complete path reaching to the near end for power control bending. Application of a small current through the nichrome wire will cause heating of the composite guide wire system which in turn will cause the dissimilar metals to bend in a selective direction. Controlling the current can cause precise bending of the guide wire, allowing one to easily manipulate the wire as it is inserted through the vessel. To change directions, this prior art guide wire can be twisted through all angle of 180 degrees or any other fraction thereof for redirecting such guide wire into a new channel within the arteries. Although such a guide wire is not slippery, it can be directed through a vessel, though resistance to the user can be a problem when a significant amount of wire remains within the arteries, possibly increasing the total time and the complexity of standard guide wire procedures.
In some cases, the prior art guide wires become resistant as they are pushed through a vessel. This can be caused by the wire passing some form of a lesion which could reduce the actual lumen of the vessel by up to 90% or conceivably block it completely. When the wire is first inserted the resistance is low but as more wire enters the vessel, there is increased contact with the inner lumen of the vessel thereby increasing the resistance. As the wire approaches blood vessel curvatures, the guide wire takes on a mind of its own. The wire's natural tendency is to stay straight in the arterial lumen. This causes the wire to ride along the outer circumference of the vessel wall while passing through it, in an attempt to find the path with the least amount of resistance. Resistance is increased because the wire has a tendency to remain straight and vessels curve. The tighter the curvature of the lumen, the more resistant the wire becomes. Surface area along the length of the guide wire increases as the wire inches forward. More than 50 centimeters into the lumen a guide wire may become noticeably more difficult to direct and passage to an occluded segment within the vessel could in some instances take a few hours, or possibly even longer, depending upon the skill or luck of the specialist.
To overcome the resistance of guide wire direction, the prior art guide wire as used may be coated with a gel or possibly coated with a Teflon-like material. These substances may decrease the total resistance of the wire. It is also possible to coat the wire with a selective genetic substance that will react with the metal composition of the wire and the inner walls of the vessel.
Coatings like the genetic or gel substances may need to be replaced several times before the wire reaches its designated site, possibly increasing the risk to the patient. Teflon materials seem to be safe when placed in the body but might not achieve total or near total reduction of wire resistance. In addition, the probability of crossing a high grade occlusion does not necessarily increase either with or without slippery coatings placed on the wire.
Still another prior art system has a guide wire with a small motor or a pnuematic device for spinning the guide wire at a significant speed. The resistance of the wire is reduced and passage of the wire through lesions is facilitated. The guide wire can also dissipate or redirect heat energy along some of the tight curves within the vessel. Heat energy applied to one particular area within the vessel can cause the guide wire to easily perforate the delicate structure of the vessel wall. In addition, the end of the guide wire has a tendency to twist and knot like a rubber band, when overly twisted, thus causing the guide wire to jam or fracture within the arterial lumen. To overcome the tangling effect of rotating devices, the guide wire is designed in a way that increases the resilience of the wire, but in turn removes the softness of the tip. These properties designed into this prior art guide wire have the problem that they increase the chance that the guide wire will drill through the vessel wall.
Another problem with this guide wire is that the wire, when spun, causes the blood to coagulate around the wire forming clots within the vessel, possibly causing cardiopulmonary damage. Clot-reducing agents, as heparin, can be used to reduce blood clotting with rotational devices, but the effect of centrifuging the blood can occur. It is possible that localize whirlpools are generated with such a spinning guide wire in the cardiovascular system. Passage, with the help of such a device seems to cause unnoticeable long term damage to the vessel, which could be the site of newly formed stenosis.